Program control for soot blowers



Sept. 8, 1959 H. P. BEARER, JR

PROGRAM CONTROL FOR SOOT BLOWER 4 Sheets-Sheet 1 Filed June 1, 1954 IA/INVENTOR.

F 6 BY M? Sept. 8, 1959 HP. BEARER, JR 2,902,707

PROGRAM CONTROL FOR SOOT BLOWER Filed June 1, 1954 Sheets- Sheet 2 P 3,1959 H. P. BEARER, JR 2,902,707

PROGRAM CONTROL FOR SOOT BLOWER Filed June 1, 1954 4 Sheets-Sheet 3 ES 4INVENTOR.

HENRY F? BEARER J cm {W wzzm Sept. 8, 1959 H. P. BEARER, JR

PROGRAM CONTROL FOR SOOT BLOWER 4 Shets-Sheet 4 Filed June 1, 1954 FIG 73nventor Fm (lttorn eg United States Patent 8 Claims. (Cl. -316) Thisinvention relates to control equipment and more particularly to controlsfor controlling the sequence of operation of a plurality of conventionalmachines, especially soot blowers.

The soot blowers which are in common use in connection with large steamgenerating boilers usually comprise a tube having radially disposed jetsdirecting steam or compressed air onto boiler tubes. The tubes of theblower are moved into position between the tubes of the boiler and airor steam from the jets blows the deposits of soot or foreign materialfrom the boiler tubes, thereby obtaining a better heat transfer.characteristic. It has been the practice to operate each individual sootblower manually. A skilled operator is needed to individually actuateeach blower and, usually, no means is provided to warn theoperator whenthe blowers are not functioning properly and to make sure that allblowers in a system have operated and that some of them have not beenoverlooked by the operator.

In overcoming disadvantages in prior soot blowers and in carrying outthe present invention, I provide an electrical circuit with a relaycommonly known as a stepping switch which controls electrical power froma common source to one soot blower or to a group of soot blowers insequence. The control I provide can also be switched so that eachindividual soot blower can be actuated individually by the operator ofthe control or the control may be connected to operate various groups ofsoot blowers in sequence.

The controller has, as its main function, the automatic selection of apredetermined sequence for operation and control of electric driven orair driven soot blower units. With. its various components, it ispossible to set up a sequence by which a series of soot blowers areoperated. It is also possible to insert all or any number of sootblowers into the sequence or manually start anyunit individually fromthe panel without running through a sequence.

When under sequence control, the controller automatically steps from onesoot blower unit, at the completion of its cycle, to the next unit inthe series. This means that the overall time duration of a completesequence has been reduced and that this time is now directly dependentupon the cumulative time of each soot blower unit.

This control system handling multiples of twenty-five units requiressmall front panel space per unit. A choice is available for the switchrequired per unit which is mounted on the front panel. It can be eithera toggle or keying switch.

The standard mounting for the program lights whether they are locking ornon-locking will be a rear illuminated, numeral engraved, larnicoidplastic sheet. The lights can be mounted as a unit behind a single sheetor separately mounted above each switch. These lights may also bemounted behind a plastic sheet, the face of which has a reproduced crosssectional view of the boiler. The

lights are mounted to denote the location of the soot blowers on theboiler.

The selector switches are shown as toggle switches and are mounted onthe panel front, there being one per machine. Three control functionsare provided for each machine unit. As illustrated, this allows the unitto be inserted into the sequence or taken out of the sequence (off) andalso provides a means for manually starting the unit.

When the selector switches are in the in sequence position, thecontroller, when started, will pick up the impulses from these switchesand send them tothe control center, energizing the motor contactor orsolenoid valve to supply power air to the air motor on air drivenblowers, thus starting the soot blower unit. The controller allows onlyone machine to operate at a time and, at the completion of the operatingcycle, the control then starts the next machine which has its selectorswitch in the sequence position. Any unit which has its selector switchin the off position is automatically bypassed.

At the same time the controller energizes the motor contactor orsolenoid valve for a particular unit, it also energizes the programlight for the corresponding unit. This 'light may be energized directlyfrom the controller, at which time it illuminates the program number forthe machine which is operating and only while that machine is operating.This light may also be energized indirectly through a relay which isenergized from the controller, at which time it illuminates the programnumber for the machine which is operating and remains energized, givingan illuminated record of the machines operated until the relays arede-energized by a clear switch.

For manual control where it is not desired to run through a sequence,the machine which is chosen to be operated individually is started bymerely depressing the selector switch lever to the manual position andholding it for several seconds until the machine starts. Upon releasingthe lever, the lever will return to the center ofi position. After theselector switch has been released, the machine selected will move toclose its limit switch 47, 48, 49, or 50 (Fig. 3) to lock in the machinecontrol and cause the machine to operate through its cycle. The manualcircuit bypasses the sequence controller and energizes the motorcontactor or solenoid valve directly.

The stepping switch is a high speed heavy duty, single motion magnetdriven stepping device with a positive non-overthrow stepping feature.It will operate in response to remote control pulses or byself-interruptions through interrupter contact springs actuated by thearmature. The switch has wipers formed with wiping tips at both ends,one hundred eighty degrees apart, which are rotated in one directiononly over a semi-circular bank of contacts.

The contact bank in actual use preferably has twentysiX points with tenlevels, giving a total of two hundred sixty contacts, ten of which areshown for each stage. 'The ten wipers, one pereach level, arenon-bridging. The switch is also provided with one set of off normalcontact springs, with a break and make combination, actuated by an armon the wiper assembly on the twenty sixth step required for homing orstopping the stepping switch on the number one contact.

The main sub-assemblies of the rotary switch are: (1) bank assembly; (2)wiper assembly; and (3) driving mechanism.

In addition to the twenty-five bank contacts partially shown as A, B, C,D, E, F, and G (Fig. 3) in each level, there is also the wiper brushspring which mounts as a twenty-sixth contact and makes electricalconnection between an associated set of wipers and the external circuitto which the wiper set is connected. This wiper brush spring extendsinward toward the wiper bearing and is so positioned and tensioned thatit makes frictional contact with the associated set of wipers. It isnecessary from a circuit standpoint to have the wiper rest on a contactin the twenty-sixth step. Therefore, an extra contact is added to allten levels which appears as the twenty-seventh bank contact in alllevels and is the last contact of each stage shown in Fig. 3. There aretwentysix steps to each half revolution.

The wiper assembly is made up of the shaft tub bear-;

ing assembly, ratchet wheel, wipers, insulators, and posi tion indicatorwheel.

Each wiper pair is made up of two wiper springs with wiping tips at oneend only. The split tips of the two springs act as twin contact springs,thus insuring double contact on each side of a back contact. These tenwipers are alternately spaced one hundred eighty de-. .grees apart.Thus, five wipers rotate over alternate levels on the first twenty-sixsteps and the other five wipers rotate over the other live alternatelevels for the next twenty-six steps.

The driving assembly consists of the driving magnet coil, a combinedarmature and stop, a driving spring, and a pawl and pawl spring. Thedriving coil is a direct current coil with a small rectifier attachment.The rectifier attachment consists of a selenium type rectifier, togetherwith an associated resistor and electrolytic condenser. A resistor isalso wired in parallel with the switch coil to provide sparksuppression.

The pawl spring is a small coiled spring pretensioned to the propervalue to cause the pawl to ride over the ratchet teeth and drop into theintervening troughs. The driving spring design is one of the majorfactors for the high stepping speed of this switch. This spring designobtains a maximum transfer of energy from the driving magnet into thedriving spring.

It is, accordingly, an object of my invention to provide a controllerfor soot blowers and other machines to be controlled in sequence whereinthe controller is simple in construction, economical to manufacture, andsimple and efiicient to use.

Another object of my invention is to provide a controlling device forcontrolling soot blowers and other machines wherein the machines arecontrolled in sequence.

Another object of the invention is to provide a controlling device formachines wherein the machines can be controlled individually or they maybe selectively controlled in sequence.

It is another object of the invention to provide a controller formachines wherein the various components may be operated in apredetermined sequence.

A further object of the invention is to provide a control circuitwherein a plurality of soot blowers is operated in a predeterminedsequence and wherein any individual soot blower or machine or pluralityof soot blowers or machines may be removed from the sequence ofoperation and any individual soot blower or other machine may beoperated manually without operating all the other blowers or machines inthe sequence.

A further object of the invention is to provide a control forcontrolling soot blowers and similar electrical and air operatedmachines in sequence wherein a plurality of similar control circuits canbe connected in series to increase the number of machines which can beoperated in sequence.

With the above and other objects in view, the present invention consistsof the combination and arrangement of parts hereinafter more fullydescribed, illustrated in the accompanying drawings and moreparticularly pointed out in the appended claims, it being understoodthat changes may be made in the form, size, proportions, and minordetails of construction without departing from the spirit or sacrificingany of the advantages of the invention.

In the drawings:

Fig. 1 discloses a soot blower of the type commonly used in connectionwith steam boilers;

Fig. 2 is a cross sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a detailed schematic wiring diagram showing how soot blowersare connected through my novel sequence control to accomplish theirpurposes;

Fig. 4 shows an additional circuit which may be used with the circuitshown in Fig. 3 as disclosed herein;

Fig. 5 is a view of the stepping switch used in my novel circuit;

Fig. 6 is a schematic View of the operating mechanism of the steppingrelay shown in Fig. 5; and

Fig. 7 is another view of the stepping relay switch.

Now with more specific reference to the drawings, by way ofillustration, I show a soot blower 1 (Fig. 1) which is of the generalcharacter of one type of soot blower which is commonly used inconnection with fuel fired steam boilers and shown for purposes ofillustration of how a soot blower or other machine may be connected in.my novel circuit. The blower unit is made up of the support 6 which mayhave the flange 7 attached thereto at 8 and has holes 9 through whichbolts may be disposed to bolt the blower 1 to a corresponding flange ofa supply pipe for a blowing medium; for example, a steam or air supplypipe.

The blower tube 5 extends through the plate 10 into the furnace. Thetube 5 is connected to the gear 12 (shown in Fig. 1) and the gear 12 andthe tube attached thereto are rotated by the motor 13 which has a pinionon the end of the shaft 14. The pinion engages the teeth 15 of the gear12 to rotate the gear and the tube attached thereto.

Cam 23 is attached to the gear 12 and is adapted to strike the follower17 to turn on the blowing medium; for example, steam or air, and causeit to flow through the tube 5 when the tube 5 is rotated to the properposition. The cam 23 lowers the follower 17 to rotate the bell crank 18around the pivot 19 and, thereby, puts a compressive force on the link20 which is connected to a valve actuating mechanism at 21 to open avalve against the force of spring 121 to turn on the steam which willflow through tube 5.

The cam 16 is likewise attached to the gear 12 which raises the follower17, rotating the bell crank 18 to shut off the blowing medium when theblower tube 5 is rotated to its proper position at the end of its cycle.

The motor 13 is connected to a source of electrical power through thecontroller 14a (shown in Fig. 3) and may be supplied power from a powersource by means of the wires 24. Other soot blowers are connected tocontrollers 14b, 14c, and 14d. The machine unit could be connecteddirectly to the wire 26a rather than through the controller 14a and,likewise, the other machines connected through controllers 14b, 14c, and14d.

The stepping switch is shown in Figs. 5, 6, and 7. The switch has a mainbody member or frame 191 which carries the contact bank assembly 102aand brushes 102. The fixed terminals 194 to which the wires leading tothe control equipment are attached are supported on frame 101. Thevarious banks a, b, c, and d of terminals A, B, C, and D are separatedby means of insulating members 117 which separate the rows of contactsfrom each other. In the preferred type of switch, there are twentyfivecontacts, five of which are shown on each stage a, b, c, and d, in Figs.3 and 5 and numbered A, B, C, and D on each stage a, b, c, and d,respectively. The letter a in Figs. 3 and 7 indicates two rows ofcontacts, contacts A, C, E, and G in one row being connected to wires82a, 82b, 82c, and 82d, respectively, through re spective wires 98a,98b, 98c, and 98d, and corresponding contacts in the adjacent row beingconnected to wires 26a, 26b, 26c, and 26d, respectively. The wiper a1and-a2 corresponding to the two rows of contacts designated a areconnected together as shown in Fig. 3 so that they, in eifect, formswitches with their contacts as they pass thereover. The shaft 120 isattached to the wiper assembly ratchet wheel 121a which is held againstreversing by the spring urged detent 122 attached to the frame 101 bymeans of screws 123.

Lever 163 is rigidly attached to armature 131. The 'magnet driving motorM is made up of the fixed solenoid 135 having the armature 131 pivotedto the frame 101 at 161. The armature 131 has the pawl 136 pivotedthereto at 132 and urged into engagement with the teeth 137 of theratchet wheel 121a by means of the coil spring 139 which is attached tothe other end of the pawl 136 at 136a and to armature 131 at 131a. Thelever 163 operates the interrupter contacts 400 upon each move- 'ment ofthe armature 131 and lever 163 to close a circuit through solenoid 46 ofrelay RS (Fig. 3). When the solenoid 46 of relay RS is thus energized bypower flowing through contacts 400, the solenoid 46 will open contact216, interrupting current to solenoid 135 and allowing the drivingspring 143 to drive the ratchet wheel 121a ahead one notch. Theadjustment of the force of the pawl 136 can be changed by means of thedrive spring set screw 144 which controls the tension on the drivingspring 143. When power is applied to the solenoid 135, it attracts thearmature 131 attached to the lever 163 to swing the armature 131 aboutpivot 161 to cause the pawl 136 to slide back over the ratchet wheel121a, thus cocking the ratchet wheel 121a. When power is interrupted tothe solenoid 135 by actuation of contact 216 through solenoid 46, thedriving spring 143 forces the pawl 136 to rotate the wheel 121a and theshaft 120 with the brushes 102 attached thereto one notch and thebrushes advance one position. At the end of movement of the lever 163,solenoid 46 will be de energized; contact 216 will close, energizingsolenoid 135 and sliding pawl 136 back over ratchet wheel 121a foranother stroke. In this manner, for each cycle of lever 163, the brushes102 of alternate stages, a, c, and e engage one contact on alternatestages a, c, and e for the first one hundred eighty degree rotation ofthe stepping switch and, therefore, the individual machine connected tothe terminal connected by the respective brush is actuated.

' Switches 47, 48, 49, and (Fig. 3) are limit switches,

one mounted on each blower. Each switch 47, 48, 49, and 50 closes itscontacts 47a to 47b and 470 to 47d as soon as the blower on which it ismounted is driven 06 its home position by its motor 13.

. In the wiring diagram shown in Fig. 3, I show the novel circuit for mycontrol. The wires 36 and 13611 representthe two sides or": a powerline, preferably 110 volts A.C. The stepping relay 101a is connectedacross .the power line by having the Wire 96 connected to the resistor51 and a rectifier 52 to the terminal 53 of the ,solenoid 135 of themotor magnet M of the stepping relay 101a. The solenoid 135 of the motormagnet M has the resistor 77 and the condenser 54 connected in paralleltherewith. The wire 55 is connected to the other side of the solenoid135 of the motor magnet M and to the normally closed contact 216 on therelay RS which is in turn connected to the push button 57 through wire58 and to the terminal 59 of the off normal spring contact S77. Theterminal 60 on the contact S77 is connected to the normally closedcontact 216 on relay RS. The terminal 60 is also connected through thewire 61 and wire 63 to terminal 641on relay RS. The other side ofsolenoid 46 on relay R8 is connected through wire 65 to terminal 66 onthe normally open is energized and, likewise, the contact 216 on relayRS is opened when the solenoid 46 of relay RS is energized. The oifnormal contact S77 is connected through wire 68 to the wire 69 which isalso connected to position I on bank a of the stepping switch. Thecircuit shown in Fig. 3 may be used to control a circuit in series withthe circuit shown when a large number of machines are to be controlled.The additional circuit will be as shown in Fig. 4 wherein the partscorresponding to the parts shown in Fig. 3 have identical numbers. Theterminals 69a, 71, 190, 80, 70, 197, 36, and 170 on the circuit shown inFig. 3 will be connected to the terminals having the same numerals inFig. 4. When wiper arm a1a2 moves to the I position, it will connect thewires 69a (Fig. 3) to the wires 71 (Fig. 4). This will have the sameeffect as pressing the start button in Fig. 3 and will cause thestepping switch 101a in Fig. 4 to advance its wiper arms one positionand will close off normal switch S177, connecting wire 68 on the circuitof Fig. 4 to the wire 71 thereon. From thence on, the relays CRA and RINwill operate the circuit shown in Fig. 4 as they did the circuit shownin Fig. 3. The additional circuit will not have to include relayscorresponding to relays RIN and CRA since the contact 88 on relay RINwill complete the circuit to the stepping switch. Since the relays RINand CRA in the circuit shown will be in the same relative position inthe additional circuit when brushes a1 and a2 complete a circuit fromwire 69 to wire 71 and the off normal contact S177 of the additionalcircuit closes to connect the circuit through wire 69, it will be seenthat the relays RIN and CRA can be deleted in the additional circuit.With the additional circuit corresponding to the circuit shown in Fig..4 connected as shown to control an additional number of machines, powerwill be supplied to the additional circuit through wire 69 through wire71 when the brush on the stepping switch shown in Fig. 8 has moved toits position I and then the machines are controlled by the steppingswitches shown in Fig. 4 in the same manner that power is supplied tothe circuit shown in Fig. 3 through the wires 13612 and 36.

The terminals 92a, 92b, 92c, and 92d are conected through theirrespective wires to terminals A, C, E, and G on the bank a of thestepping switch 101a. Terminals A, C, E, and G are selectively connectedby brushes a1 and a2 through wires 99a, 99b, 99c, 99d, 26a, 26b, 26c,and 26d to the respective operating mechanisms 14a, 14b, 14c, and 14dwhich represent the operating contactors on various machines which areto be operated. The motors of the machines to be operated could beconnected directly to the respective terminals 13a, 13b, 13c, and 13dwithout going through the contactors 14a through 14d, if so desired. Theterminals 13a, 13b, 13c, and 13d could be connected to the terminals ofthe solenoids of solenoid operated air valves for air operated machines.The control disclosed also has utility in operation of many other typesof machines for other purposes where a sequence or program control isrequired. Banks a, b, c, and d comprise first, second, third, and fourthbanks of contacts, respectively. CRA, RIN, and RS comprise first relays,second relays, and third relays as referred to in the claims herein.This convention is adhered to except in claim 8 wherein bank 0 isreferred to as a second bank.

The wires 82a 82b, 82c, and 82d are also connected to the terminals A,C, E, and G of the bank b on the stepping switch 101a through wires 62athrough 62d whereby the brush b1 rotates with the rotating mechanism onthe stepping switch to connect the points A, C, E, and G to the solenoid83 and through wire 86 to the other side of the line 13Gb. Wire 84 isalso connected to one side of the solenoid 83 of the relay CRA and toone side of the solenoid 87 of the relay RIN. The normally open contact88 on the relay RIN connects through the wire 89 to the common terminal90 on the bank 0 of the stepping relay101a. The wire 91 is connected tothe terminals A, C, E, and G of stage of the stepping relay 101a. Itwill be seen that when the selector switches 35a, 35b, 35c, and 35d aremoved to the S or sequence position so that they connect wire 80 toterminals 92a, 92b, 92c, and 92d, wires 82a through 82d to terminals A,C, E, and G on bank a of the stepping switch 101a, the circuit will beset for sequence control. When any of the selector switches 35a through35d are in the position, with switch terminals 250a through 250dconnected to wires 93a through 93d, respectively, current will flow fromthe wire 36 through the normally closed contact 78 through the resetterminal 79 through the selector switches which are in the manualposition through the wires 93a to 93d which are connected to a closedselector switch through wires 26:; through 26d directly to the controlmembers 14a through 14d whereby the control members will be operated tostart the machine connected thereto.

The indicating lights 39a through 39d are connected through theirrespective wires to terminals A, C, E, and G of the bank d of thestepping switch 101a whereby they are lighted when the stepping switch101a rotates through these various positions and the lights indicate therespective position to which the stepping switch is moved and,therefore, indicate which one of the control members 14a through 14d isenergized.

With brushes a1, a2, b1, c1, and d1 in the 0 position, the steppingrelay 101a is started by closing push button 57. This completes thecircuit from wire 36 through the normally closed contact 78, contact 76,stop button 75, wire 37, wire 68, contact S77, wire 95, push button 57,and normally closed interrupting contact 216 to solenoid 135 throughrectifier 52, resistor 51, and line 96 to the other side of the line1361;. The solenoid 135 being energized, it closes its armature 163 anddraws back its lever 131 which in turn closes interrupter contact 400,completing the circuit to solenoid 46 of relay RS and energizing it.Relay RS is connected in parallel with solenoid 135 in order to providea time delay in the action of the stepping relay to allow the mechanicalparts of the system to function at the time intervals between the stepsof the stepping relay. The normally closed contact 216 on relay RS thenopens, breaking the circuit to solenoid 135 of the motor magnet M,deenergizing the solenoid 135, and allowing spring 143 to move thearmature 163 to the open position, causing the pawl 136 to rotate theratchet wheel 121a one notch, thus stepping the unit one step and movingbrushes a1, a2, b1, c1, and all to the A position. At this time, offnormal contact S77 is closed by a cam 91 actuated on wheel 121a by themovement of the rotor of switch 191a on which it is attached, breakingthe circuit to wire 95 through wire 212 and to indicating light 211.Light 211 will extinguish, signifying the unit is in operation. Acircuit will be closed from control power wire 36 to relay solenoid 46.Simultaneously with this first step of the stepping switch 101a, brushesa1, a2, b1, 01, and d1 all rotate one step to position A. At this sametime, if selector switch 35a is in the sequence position, that is, withterminals 92:! in engagement with contact 250a, the circuit is completedfrom wire 36 through closed contact 78 and closed contact 79 throughwire 80 through terminal 92a to wire 82a to the first bank a. Thecircuit is also completed from wire 82a through wire 62a to terminal Aon bank b through brush [)1 through wire 97 to solenoid 83 and wires 85and 86 to the other side of the line 136b, energizing solenoid 83.Solenoid 83, upon being energized, breaks its normally closed contact 76between wire 36 and the solenoid 135, stopping the stepping switch 101a.Solenoid 87 of relay RlN is energized to close contact 88 thereon at atime when brush c1 on bank 0 is in one of the positions A, C, E, or Gand when one of the limit switches 47, 48, 49, or is closed.

If the selector switch a had been in the manual posi- 8 tion withcontact 250a connected to wire 93a, power would have flowed from wire 36through Contact 78, contact 79, wire 80, contact 250a, Wire 93a, andwire 26a to controller 14a, energizing it. It is held energized by limitswitch 47 until the machine completes its operation. Therefore, bysnapping any switch 35a35d to the manual position in, the correspondingsoot blower will be operated individually through one cycle.

Further, if any of the switches 35a through 35a, for instance, 35b, isin the oif position and the other switches are in the automatic positionand the control is set for sequence operation, no power could flow tocontroller 14b from wire 80. When the stepping switch moves the brush b1to the C position, since no power could flow rom wire 36 through wirethrough contact C of stage b, solenoid 83 of relay CRA would not beenergized to open its contact 76, interrupting the flow of power to thesolenoid of the stepping switch 101a. Therefore, the relay CRA operatedthrough terminal 92d would not operate. Therefore, the stepping switchwould continue to step until brush b1 rested on one of the contacts A,C, E, or G which connected to a switch 35a through 35d which was closedto the sequence position. That is, power to the stepping switch wouldnot have been interrupted by contact 76 on relay CRA and the steppingswitch would continue to step until brush b1 engaged a contact A, C, E,or G thereon connected to a switch 35a through 35d which was closed tothe sequence position.

Switches 47, 48, 49, and 59 are limit switches, one on each machine,mounted inside housing 2A and actuated by screw 2 which extends throughthe gear 12 at 23, this screw being one of those holding cam 16 in placeon gear 12, and engages actuating member 2C when the gear 12 startsrotating to a predetermined position. Each limit switch is actuated whenthe respective machine on which it is mounted is started. When themachine to which power is applied by the control starts its operation,then the machine screw 2 rides oif of limit switch 47 or 48 or 49 or 50and the limit switch closes, locking the circuit closed from wire 36 towires 26a, 26b, 26c, or 26d to controller 14a or 1412 or 14c or 14d andalso completing the circuit from wire 36 to solenoid 87 of relay RIN.The respective limit switch which is closed by a machine will keep themachine operating until it has completed its cycle and the screw on cam16 on gear 12 opens the limit switch on the machine. The solenoid ofrelay RIN is energized through the switch 47 or 48 or 49 or 50 which isclosed by a machine through wire 170. Relay RIN, when energized, closesits normally open contact 88 connecting wire 36 therethrough to brush01, through its bank contact and wire 91, through wire 37, closedcontact 60 of contact S77, and contact 216 to solenoid 135 of motormagnet M which again energizes relay RS, opening contact 216 andallowing driving spring 143 to step the switch one step to bring brushesa1, a2, b1, 01, and d1 to their B position. In stepping the switch tothe B position, contact is broken through the brushes a1, a2, b1, and Cland to the elements connected which means that the soot blower energizedis held energized only by the limit switch. With the brush b1 inposition B, relay CRA will be de-energized and it will open. Blush c1will also be in an open position. When the stepping relay moves brush[21 to any of the closed positions A, C, E, or G, brush d1 completes acircuit from wire 36, through wire 232, through the bank contact A, C,E, or G to wire 86, and to program indicating lights 39a, 39b, 390, or39d. This program light indicates that a particular machine isoperating. The machine being operated, for example, by contactor 14a,completes its cycle and the limit switch rides upon its cam 2B on gear12, opening the circuits to contactor 14a, dropping it out of thecircuit. At the same time, it also breaks the circuit to the solenoid ofrelay RIN.

As soon as relay RIN opens, it closes its contact 78,

mower completing the circuit between wire 36, through contact 76, stepbutton 75, through terminal 60 on ot tnormal spring contact S77, throughclosed contact 216, and'to the solenoid 135, energizing motor magnet Mwhich draws back the pawl 136, closing interrupter contact 400. Thesolenoid 46 of relay RS is energized which in turn opens normallyclosedcontact 216;. This de-energizes solenoid. 135, allowing driving, spring143 to. step the stepping switch 101a over to the third step to startanother machine. i p

-Ifi one of'theselector switches 35a through 35d for a particular unitis not-in the automatic'position, the circuitlfrom wire 36through-wire80- tothe bank contacts Aer Cor'Eor G on bank bwill remain opendepending upon which selector'switch is not in the automatic position.-The circuit thus is open from wiper b1 to the solenoid 83 of relay CRA.The stepping relay 101a will continue to step until brush b1 againreaches a bank contact A or C or E or G on bank b which is connectedthrough one of the selector switches 35a to 35d to wire 80. This willcomplete the circuit through brush b1 and wire 97 to the solenoid 83 ofrelay CRA, energizing it, which in turn opens its normally closedcontact 76, breaking the circuit between wire 36 and contact 60 to thesolenoid 135, stopping the stepping switch 101a.

The stepping switch 101a will continue to step as long as the normallyclosed contact 78 of relay RIN and contact 76 of relay CRA are closed,completing a circuit between wire 36 and off normal contact S77. When aselector switch is put in the sequence position, the stepping switch101a through brush b1 will complete a circuit to solenoid 83 of relayCRA opening its contact 76, thus stopping the stepping switch. Contacts201 and 79 are preferably operated by a push button which allows theoperator to re-position the stepping switch 101a from any place in itscycle back to the home position by breaking the circuit between wire 36through wire 80 to selector switches 35a to 35d. Simultaneously, itcloses the circuit through wire 37, contact S77, and normally closedcontact 216 to solenoid 135, automatically stepping the stepping switch101a back to the home position where the switch allows contact S77 toopen, breaking the circuit to the stepping switch 1010:.

The numbers of the stepping switch positions A, B, C, D, E, F, G, H, andI may be increased to any practical number, depending upon the size ofthe stepping relay. The number of machines which can be controlled bythe system may be increased by providing other stepping relays in seriessuch as that connected to the wires 70 and 71 as explained above.

In the foregoing specification, I have set forth the invention in itspreferred practical forms but I am aware that the structure shown iscapable of modification within a range of equivalents without departingfrom the invention which is to be understood is broadly novel as iscommensurate with the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In combination, a sequence circuit and a plurality of soot blowersfor blowing foreign material from heat transfer surfaces of a steamboiler comprising a source of electrical'power, a stepping switch havinga motor, a first and a second relay, said stepping switch having a firstbank and a second bank of contacts and wiper contact arms for each bankmovable in unison by said motor, said first bank comprising spacedswitches, one side of some of said switches being each connected to oneof said soot blowers, the other side of said switches being connectedthrough a normally closed contact on said second relay to said powersource, said first relay having a motor connected to said wiper arm onsaid second bank, the side of said switches on said first bank connectedto said normally closed contact being connected to corre spondingcontacts on said second bank, said first relay 10 having a normallyclosed contact connected between said normally closed contact on saidsecond relay and said stepping switch motor, said soot blowers eachhavinga limit switch thereon, said second relay having a motor,- saidlimit switches'connecting said second relay motor to said power sourceto open said normally closed con-' tact thereon each timea soot bloweris initially connecte through a switch on said first bank to said powersource, means connecting said soot blowers'to said power source afterthey have been initially connected thereto for maintaining theconnection of said soot blower to said power source, and means connectedin parallel with said relay contacts toconnect said stepping switchmotorto said power source to cause said stepping switch motor to movesaid wiper arms temporarily 'to-advanced open contact positions after asoot-blowerhas started.

2. The combination recited in claim 1 wherein said means connected inparallel with said relay contacts to connect said stepping switch motorto said power source when said first relay contact is open comprises athird bank of contacts on said stepping switch, a wiper for said thirdbank of contacts, some of said contacts on said third bank beingconnected to said stepping switch motor, said wiper arm on said thirdbank being connected to said power source through a normally opencontact on said second relay.

3. The combination recited in claim 2 wherein said means for maintainingeach said soot blower connection to said power source comprises a secondlimit switch on each side soot blower connecting said soot blower tosaid source of power through its entire cycle after said soot blower hasbeen started by connection thereof to said source of power through saidfirst bank of switches and said second relay normally closed contact.

4. The combination recited in claim 3 wherein each said switch on saidfirst bank of contacts is connected to said normally closed contact onsaid second relay by means of a double throw switch whereby each saidsoot blower can be selectively and individually connected to said powersource.

5. The combination recited in claim 4 wherein a third relay is provided,said third relay having a solenoid connected in series with a normallyopen contact on said stepping switch and a normally closed contact inseries with said stepping switch motor whereby said stepping switchmotor is deactivated when said third relay is actuated and vice versa,thus introducing a time delay in the.

action of said stepping switch motor.

6. The combination recited in claim 1 wherein an additional bank ofcontacts is provided on said stepping; switch, said additional bank ofcontacts having a wipercontact arm on said stepping switch driven bysaid step-- ping switch motor and connected to said power source,.spaced contacts in said additional bank being connected to indicatinglights for respective blowers, said wiper con-- tact arm engagingsuccessive ones of said spaced contacts during the blowing cycles oftheir corresponding blowers.

7. The combination recited in claim 1 wherein a reset switch is providedhaving normally open contacts conmeeting said power supply to saidstepping switch motor, said reset switch being operable to complete acircuit to said stepping switch motor to supply power thereto to drivesaid stepping switch motor to a neutral position.

8. In combination, a sequence control and a plurality of soot blowersfor blowing foreign material from the heat transfer surfaces of a steamboiler comprising a source of electrical power, a stepping switch havinga first, and a second bank of contacts, said stepping switch having amotor thereon, a wiper contact arm on said stepping switch driven bysaid motor, a relay having a normally open and a normally closed contactand a solenoid thereon, said first bank of contacts comprising spacedswitches, one side of some of said switches being each connected to oneof said soot blowers, the other side 0t said switches being connectedthrough said normally closed contact on said relay to said source ofpower, said stepping switch motor being connected to said source ofpowerthrough said normally closed contact on said relay, and limitswitches on each said soot blower, each said limit switch closing when,the soot blower on which it is supported is energized and opening whenthe soot blower returns to. normal position, one said limit switch oneach said soot blower connectingsaid relay solenoid to said source ofpower, the other said limit switch connecting the soot blower on whichit is. mounted to said source of power, the normally open contact onsaid relay being connected in series between said power source and awiper arm on said second bank of contacts, some of said contacts on saidsecond bank being connected to said stepping switch motor and other saidcontacts being unconnected whereby said stepping switch will be moved toadvanced open contact position and de-energized while any said sootblower is blowing.

References Cited in the file of this patent UNITED STATES PATENTS2,396,422 Hines Mar. 12, 1946 2,579,983 Thornton Dec. 25, 1951 FOREIGNPATENTS 491,915 Great Britain Sept; 8, 1938 529,306 Great Britain Nov.19, 1940 529,598 Great Britain Nov. 25, 1940 597,779 Great Britain Feb.3, 1948 651,553 Great Britain Apr. 4, 1951 669,388 Great Britain Apr. 2,1952

